[ntp:questions] best gps receiver for time synchronization

Kevin Oberman oberman at es.net
Wed Mar 11 23:50:09 UTC 2009

> From: Dave Hart <davehart at gmail.com>
> Date: Tue, 10 Mar 2009 08:56:14 -0700 (PDT)
> Sender: questions-bounces+oberman=es.net at lists.ntp.org
> On Mar 10, 3:44 pm, "Richard B. Gilbert" <rgilber... at comcast.net>
> wrote:
> > You might want to take a look at the work of Poul-Henning Kamp (PHK).
> > He used Soekris 4501 single board computers together with a GPS receiver
> > to make a highly accurate clock.  This was long enough ago that most of
> > the hardware he used is no longer available new but it might give you
> > some ideas.
> Seconded.  FreeBSD will give you better timekeeping than Windows.  If
> the difference between a few microseconds and a few hundred
> microseconds is no problem, my recent Windows releases are fine.  But
> if you're dedicating a small PC to the task, care about those
> fractions of a millisecond, and can manage FreeBSD, it's the gold
> standard for NTP.

To get an idea of the fanaticism involved, several years ago, Kirk
McKusick and my former boss here in Berkeley counted the machine cycles
in the FreeBSD kernel for the PPS response(all done in the interrupt
service routine) and used that to correct the time. Of course,in the
days of 16 and 40 MHz systems, this was a bit more important.
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751

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